SAN FRANCISCO (KRON) – Centers for Disease Control and Prevention Director Dr. Rochelle Walensky said data suggests people who have been fully vaccinated do not carry COVID-19.

Walensky made the revelation during an interview with Rachel Maddow Monday, adding that “it’s not just in the clinical trials but it’s also in real-world data.”

A CDC study released Monday showed that mRNA vaccines Moderna and Pfizer are 90% effective at preventing COVID-19 infections after two doses.

“This is very reassuring news,” said the CDC’s Mark Thompson, the study’s lead author. “We have a vaccine that’s working very well.”

Walensky also spoke about the “impending doom” comments she made during a virtual White House briefing, in which she warned of a potential fourth wave of the virus.

“We have so much to look forward to, so much promise and potential of where we are and so much reason for hope,” she said. “But right now, I’m scared.”

“I’m going to lose the script, and I’m going to reflect on the recurring feeling I have of impending doom,” she said.

Walensky said she was optimistic about the increasing rate of vaccinations in the U.S. but said challenges remained over distribution in the coming weeks.

“You know, we have been vaccinating our people over the age of 65, those are the people that have accounted for 80 percent of the deaths so far, that we’ve done so well in vaccinating the more senior members of our society that deaths might not be what we would expect with prior surges. It’s also the case, though, that, you know, if we don’t see those number of deaths, the deaths that we’re going to see is among younger people,” Walensky told Maddow. “Obviously, we don’t want to see those either.”

At last check, more than four million vaccines had been administered in the Bay Area. You can check your county’s vaccination distribution numbers here.